The black tint, Ensemble: Black Flight’s Vestments, is a reward for completing Chapter 5 of the Zaralek Caverns campaign, which focuses on major Black Dragonflight characters. The other four tints are currently unimplemented in game, but seem to align with the colors of the other Dragonflights.
This armor set could also be inspired by Wrathion’s shoulders, which feature many small scales creating interesting textures.